Batteries gradually deteriorate due to various factors such as the change of using environment and the increase of number of charging/discharging cycles. During the deteriorating process, various measuring tools are used to measure degradation parameters of the battery to determine whether the battery is still suitable for use.
Some techniques have been proposed for measuring the battery degradation parameters, for example, in US Patent Application Publication No. 2011/133744, U.S. Pat. No. 6,832,171, U.S. Pat. No. 6,433,513 and JP Patent Application Publication No. 2007-178333. US Patent Application Publication No. 2011/133744 utilizes an interference source to detect an internal resistance of a battery and thereby determine degradation degrees of the battery. However, in this method, an additional device is required to generate the interference source, which increases the system hardware cost.
In addition, U.S. Pat. No. 6,832,171 detects a remaining available capacity and capacity degradation information of a battery by recording an impedance curve of the battery. Besides, U.S. Pat. No. 6,433,513 determines the degradation degrees of a battery and predicts its service life based on a charged amount corresponding to a voltage period of the battery during charging. However, both above methods require a huge table to be established for recording or calculating the degradation degrees and a continuous update of the recorded data, thereby increasing the system complexity.
In JP Patent Application Publication No. 2007-178333, when the battery is switched from a constant current charging to a constant voltage charging, the battery is first rested for a period of time and a voltage change rate of the battery is measured to thereby detect the degradation degrees of the battery. However, in this method, the charging operation of the battery is required to be interrupted to measure the battery degradation.